1. Field of the Invention
The present invention relates to a magnetic head apparatus to be used in flexible disk drive apparatus and others.
2. Description of the Prior Art
For instance, the Japanese Patent Laid-Open No. 61-39910 discloses a magnetic head to be employed for a flexible disk drive apparatus. FIG. 3 shows the magnetic head 1 illustrated in this publication, wherein numeral 2 represents a write/read core assembly including a L-shaped core 2a, an I-shaped core 2b and a back core 2c so as to constitute a closed magnetic circuit, the L-shaped core 2a and the I-shaped core 2b forming a write/read gap on a sliding surface, and numeral 3 designates a write/read coil wound around the L-shaped core 2a of the write/read core assembly 2, the write/read coil constituting a write/read head 4 together with the write/read core assembly 2. Further, numeral 5 denotes an erasing core assembly including a L-shaped core 5a, an I-shaped core (the I-shaped core 2b making up the aforementioned write/read core assembly 2), a back core 5c so as to constitute a closed magnetic circuit, the I-shaped core 5b forming an erasing gap on the sliding surface in conjunction with the L-shaped core 5a. Still further, numeral 6 is an erasing coil wound around the L-shaped core 5a of this erasing core assembly 5 which, in cooperation with the erasing core assembly 5, constitutes an erasing head 7.
As illustrated in FIG. 4, the magnetic head 1 thus constructed is operable such that the erasing head 7, preceding the write/read head 4, slides with respect to a track surface of a magnetic disk 8 along the rotational direction of the magnetic disk 8 so as to reproduce information on a recording track 9 or record information on the recording track 9. Furthermore, as shown in FIG. 5, for the magnetic disk 8 in which both surfaces are respectively used as track surfaces 8a and 8b, a magnetic head apparatus comprising a pair of magnetic heads 1a and 1b such as illustrated in FIG. 3 is used to perform the recording/reproducing operation.
On the other hand, in the case of reproducing information from the magnetic disk 8 by using the magnetic head shown in FIG. 3, in order for preventing occurrence of crosstalk at the write/read coil 3 on the basis of variation of the magnetic flux due to the recorded information on the magnetic disk 8 which appears at the erasing gap, the erasing coil 6 can be coupled in parallel to a crosstalk preventing element such as an inductance element as disclosed in the Japanese patent Application No. 2-41211.
Thus, in the case that an arrangement that provides a crosstalk preventing element to prevent a crosstalk to be generated by the erasing coil 6 at the time of the reproducing mode is applied to a magnetic head apparatus comprising a pair of magnetic heads as illustrated in FIG. 5, a device as illustrated in FIG. 6 is proposed in the Japanese Patent Application No. 2-41211. In FIG. 6, 3a and 3b respectively represent first and second write/read coils of first and second magnetic heads 1a and 1b, 6a and 6b respectively designate first and second erasing coils of the first and second magnetic heads 1a and 1b, 10 denotes a mode selection circuit which is responsive to a magnetic head selection signal A for selecting one of the first and second magnetic heads 1a, 1b and further to responsive to an operation mode signal B for selecting one of the recording and reproducing modes so as to output a switching signal, and 11a depicts a first switching control means which is responsive to the switching signal from the mode selection circuit 10 so as to control the above-mentioned first write/read coil and first erasing coil 6a. The first switching control means 11a is activated when the magnetic head selection signal A is indicative of the selection of the first magnetic head 1a and arranged to cause a recording current corresponding to the information to flow through the first write/read coil 3a and cause a constant current to pass through the first erasing coil 6 a when the operation mode signal B is representative of the recording mode and further arranged to output the read voltage obtained through the first write/read coil 3a at the time of the reproducing mode. Further, 11b represents a second switching control means which is responsive to the switching signal from the mode selection circuit 10 so as to control the above-mentioned second write/read coil 3b and second erasing coil 6b. The second switching control means 11b is activated when the above-mentioned magnetic head selection signal A is indicative of the selection of the second magnetic head 1b, and arranged to cause a recording current corresponding to the information to flow through the second write/read coil 3b and cause a constant current to pass through the second erasing coil when the operation mode signal B is representative of the recording mode and to output the read voltage obtained through the second write/read coil 3b at the time of the reproducing mode. Still further, 12a and 12b respectively represent read amplifiers which are responsive to the read voltages from the above-mentioned first and second switching control means 11a and 11b so as to amplify the read voltages therefrom, 13a and 13b are first and second crosstalk preventing elements each of which comprises an inductance element and which are respectively provided with respect to the first and second erasing coils 6a and 6b of the first and second magnetic heads 1a and 1b, 14a and 14b are switching elements each of which is composed of a transistor element and which are respectively coupled in series to the first and second crosstalk preventing elements and coupled in parallel to the first and second erasing coils 6 a and 6b corresponding thereto. The first and second switching elements 14a and 14b are responsive to the above-mentioned operation mode signal B so as to be deenergized when the operation mode signal B is indicative of the recording mode and energized when being representative of the reproducing mode.
Secondly, a description will be made hereinbelow in terms of the operation to the magnetic head apparatus thus arranged. First, let it be assumed that the magnetic head selection signal A is representative of the selection of the first magnetic head 1a and the operation mode signal B is indicative of the recording mode. Thus, the first switching control means 11a is activated and the recording mode is set. At this time, the second switching control means 11b is in the non-activated state and the first and second switching elements 14a and 14b are respectively in the deenergized states. In response to the first switching control means 11b being activated and the recording mode being set, the first switching control means 11a causes the recording current corresponding to the information to flow through the first write/read coil 3a and further causes the constant current to pass through the first erasing coil 6a. As a result, the information previously recorded is erased from the first track surface 8a of the magnetic disk 8 by means of the first erasing coil 6a and information is recorded on the erased track by the first write/read coil 3a.
On the other hand, in response to the operation mode signal B being indicative of the reproducing mode, the first switching control means 11a is set to the reproducing mode so as to detect the reproduced voltage corresponding to the information recorded on the first track surface 8a of the magnetic disk 8 which reproduced voltage is developed at the first write/read coil 3a, the detected reproduced voltage being outputted to the first read amplifier 12a. At this time, the first and second switching elements 14a and 14b respectively enter into the energized states by the operation mode signal B indicative of the reproducing mode. Accordingly, a current flows through the first erasing coil 6a on the basis of the information recorded on the first track surface 8a of the magnetic disk 8 and a back electromotive force is developed in the first crosstalk preventing element 13a, coupled in parallel to the first erasing coil 6a, in accordance with the current, so that the back electromotive force causes a cancelling magnetic flux to generate in the first core assembly 5 so as to cancel the magnetic flux which is developed on the basis of the information recorded on the first track surface 8a of the magnetic disk 8, thereby suppressing the generation of the crosstalk in the first write/read coil 3a.
Furthermore, let it be assumed that the magnetic head selection signal A is representative of the selection of the second magnetic head 1b, the second switching control means 11b is activated and the first switching control means 11a enters into the non-activated state. Moreover, the second switching control means 11b is set to the recording or reproducing mode in accordance with the operation mode signal B so as to control control the second write/read coil 3a and the second erasing coil 6b to effect the recording and reproduction as well as the case that the above-mentioned first switching control means 11a is activated. Accordingly, in the case of being arranged as illustrated in FIG. 6, although in the reproduction due to the first magnetic head 1a it is possible to suppress the crosstalk generated in the first write/read coil 3a by the magnetic flux developed at the first erasing core assembly 5, a current flows through the second erasing coil 6b of the second magnetic head 1b due to the information recorded on the second track surface 8a of the magnetic disk 8 and hence a back electromotive force occurs by the second crosstalk preventing element 13b so that a cancelling magnetic flux is generated in the second erasing coil 6b. There is a problem that the cancelling magnetic flux is leaked as the crosstalk to the first write/read coil 3a. Similarly, in the case of the reproduction of the second magnetic head 1b, there is a problem that the cancelling magnetic flux generated in the first erasing coil 6a due to the first crosstalk preventing element 13a is leaked as the crosstalk to the second write/read coil 3b which is in the reproducing state.